Yeah, this is merely the entrance, or one of them anyway. Since it is built in a mountain range, much of its chambers and catacombs would be underground, and since it's mostly full of dead people and occasionally a couple of elves, it doesn't need a big harbour, surrounding farms or trade routes.
Maybe one day I'll make a bigger version, although when it comes to buildings I mostly build them as set pieces for battles and remove them again later. Sometimes, I have put quite a bit of effort into the battlefield, in Siege of Reichingrad particularly. But functionality in a BrikWars setting is always the main goal, which means, you gotta be ready to blow that stuff up, too.
One problem I have is that I have difficulty imagining how I would even build a more complicated castle (even though I have visited many), since you'd really have to build the terrain first. A lot of the builds I find online for inspiration are either unrealistically complicated, or rely on massive amounts of a single type of brick (which I don't have) to create a certain terrain feature, which doesn't help me much. When I made a 'bigger town' (Andelmere) my approach was to basically put a bunch of separately constructed buildings together in a way that made sense. Which is, I guess, how castles were built.